The capital went into one of its frequent paroxysms of scandal this week after Rep. Michael Grimm of New York became the third member of the House Republican majority to get into trouble recently.

First there was the "cocaine congressman," Trey Radel of Florida, who resigned in January after pleading guilty to drug charges related to his attempt to buy cocaine from an undercover agent.

Then came the "kissing congressman," Rep. Vance McAllister of Louisiana, caught on film kissing a staff member not his wife. He announced Monday that he would not seek re-election, even though he said, "I don't have no regrets at all."

And now we have what might be called the "quinoa congressman," Grimm. The former health-food restaurateur was hit with a 20-count federal indictment Monday accusing him of employing illegal immigrants and evading taxes by hiding $1 million in revenues at his restaurant, Healthalicious.

It is a sign of just how commonplace scandal has become that House Speaker John Boehner, in a news conference Tuesday morning, declined to call for Grimm's resignation, saying only that Grimm made the "right decision" to give up his committee assignment, a modest gesture from a member of Congress facing charges carrying a combined maximum of more than 200 years in prison. The speaker answered reporters' questions tersely and then walked away, muttering, "So much fun. So much fun."

Misbehavior by public officials is depressingly routine. But the latest cases are instructive because the alleged transgressions or missteps began either before the lawmaker came to Washington (in Grimm's case) or soon after arriving in Washington (McAllister was filmed a month after he was sworn in, and Radel was arrested 10 months after taking the oath of office). They weren't in Washington long enough to have been undone here.

This is crucial evidence in the-chicken-or-the-egg, nature-vs.-nurture debate about what makes politicians go bad. Are they upstanding people polluted by Washington's ways? Or is there something wrong with the type of person who runs for Congress in the first place?

The latest data points suggest fault rests on voters in the 50 states and 435 districts that send their representatives here. Perhaps politics attracts those with an inflated sense of self who feel exempt from the usual rules. It's also possible that Congress actually does look like the United States, except individual flaws here are magnified because of the scrutiny. Assemble any random group of 535 Americans and you're bound to find a few drug users, perverts, crooks and clowns.

When Radel, elected in 2012, was charged last year, prosecutors said the Oct. 29 cocaine purchase that prompted his arrest was just the latest of "several." In a statement after the matter became public, the 37-year-old Radel blamed "the disease of alcoholism" for his poor judgment — and, if so, such a condition was unlikely to have developed entirely in the 10 months since he was sworn in.

McAllister's downfall came even faster. He was sworn in on Nov. 21, 2013. Two months later, he told constituents at a Chamber of Commerce luncheon that his job "sucks." In between, a surveillance camera caught him turning out the lights in his office and passionately kissing the staffer, who had been paid to clean his campaign office; the video leaked this month.

McAllister, in deciding not to seek re-election, was a model of contrition compared with Grimm, who famously threatened a reporter with violence after the State of the Union address. After his indictment Monday on mail and wire fraud and other charges, Grimm declared himself the victim of a "political witch hunt."

There's no way Grimm's alleged wrongdoing can be blamed on Washington. The rot at Healthalicious is alleged to have occurred between 2007 and 2010, before Grimm arrived here. (A separate matter, involving questionable campaign contributions he got from followers of a mystical rabbi, also predates his arrival.) But he's Washington's problem now, as his taint spreads to his party and Congress and confirms Americans' disgust with their government.

Returning to the Capitol Tuesday, Grimm displayed the same brazenness that got him into trouble in the first place. He told reporters he's "absolutely not" resigning and is "back to work," as if detained by nothing more than a flight delay. Later, arriving on the House floor for a vote, he announced to reporters that "I've already given my comment," and then, grinning, the quinoa congressman walked into the chamber to vote.

Dana Milbank is a Washington Post columnist. Email him at danamilbank@washpost.com. Follow him on Twitter @Milbank.